Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Human-Human Sensorimotor Interaction(2019) Honarvar, Sara; Shim, Dr. Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We investigated the role of sensory feedback in inter-personal interactions when two co-workers are working together. Twenty-five co-workers completed two isometric finger force production experiments. In Experiment 1, co-workers isometrically produced finger forces such that combined force will match a target force and/or torque under different visual and haptic conditions. In Experiment 2, without participants’ knowledge, each performed the same task with the playback of his/her partner’s force trajectory previously recorded from Experiment 1. Results from both experiments indicated that co-workers performed the task worse in the presence of haptic and visual feedback. Since, in latter as opposed to the former condition, they adopted a compensatory strategy to accomplish the task accurately. Further analysis showed that co-workers achieved the same level of motor performance with similar control strategies, suggesting that they did not work synergistically to achieve better performance, but one co-worker processed another as disturbance when they worked together.Item Small molecule inhibitors of cyclic di-AMP signaling(2018) OPOKU-TEMENG, CLEMENT; SINTIM, HERMAN O; JULIN, DOUGLAS; Biochemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Globally, it is estimated that more than 700,000 people die annually from infections caused by drug-resistant bacterial pathogens. Resistant strains of bacteria continue to be isolated in healthcare and community settings. At the same time, the antibiotic pipeline remains dry – exemplified by the paucity of new antibiotics introduced into clinical use. Consequently, antibiotic-resistant strains are rapidly spreading, and antibiotic-resistant infections persist. Additionally, the existing antibiotics target one of the common targets – DNA, RNA, protein and cell wall synthesis. There is an apparent need to identify antibacterial agents against novel targets to slow down the generation of resistance. Cyclic dinucleotides have emerged as central regulators of bacterial physiology. Particularly, cyclic di-AMP (c-di-AMP) regulates cell wall homeostasis, cell size, potassium ion transport, virulence and biofilm formation in various Gram-positive pathogens including Staphylococcus aureus, Enterococcus faecalis, Listeria monocytogenes and Streptococcus pneumoniae. It has been demonstrated that under standard laboratory conditions, deletion of the diadenylate cyclase genes that encode c-di-AMP synthesizing enzymes (diadenylate cyclase, DAC) was lethal in human pathogens like S. aureus and L. monocytogenes. Hence, DACs have been suggested as potential antibiotic targets. Thus far, the effect of c-di-AMP on bacterial physiology has been studied using genetic approaches whereby the key players of the second messenger signaling are deleted, inactivated or overexpressed to create conditions of varying intracellular c-di-AMP levels. However, these approaches are not amenable to drug development. Cell permeable small molecule modulator or c-di-AMP levels are required to validate the druggability of c-di-AMP signaling. This dissertation reports the identification of different small molecules that potently inhibit c-di-AMP synthesis. The cell permeable inhibitors possess the ability to decrease the intracellular concentration of c-di-AMP. Furthermore, the antibacterial activities of the cell permeable c-di-AMP synthesis inhibitors have been characterized. Efforts towards the development of antibiotics have also been discussed.Item Muscular Fatigue Influences Motor Synergies During Push-ups(2018) Bell, Elizabeth M; Shim, Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research used the push-up as an experimental paradigm for the study of adaptations in motor synergies throughout the challenge of muscular fatigue. Fatigue was expected to lead to greater synchronization of power production (greater motor synergy) by the Central Nervous System (CNS). Greater between and within-limb synergies would be necessary to overcome the reduced force production of fatigued muscles. Different changes in joint power synergies were expected for eccentric and concentric phases due to muscle properties and direction of gravity. Eleven subjects performed push-ups repetitions to self-selected failure. Subjects initially performed push-ups using positive between and within-limb joint power synergies, however synergies reduced throughout reps. Congruent with hypotheses, between and within-limb synergy reduced at a lesser rate throughout eccentric movements. The strategy used relied on bilateral elbow and shoulder joint production. The CNS was not able to adapt control strategies, but instead the dominant strategy was affected throughout fatigue.Item Handwriting Kinetics: A Search for Synergies(2008) Hooke, Alexander W.; Shim, Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this study was to investigate central nervous system strategies for controlling multi-finger forces in three-dimensional (3-D) space during a circle drawing task. In order to do this the Kinetic Pen, a pen capable of measuring the six-component force and moment of force that each of four individual contacts applies to the pen during writing, was developed. The synergistic actions of the contact forces, defined as kinetic synergy, were investigated in three orthogonal spaces: radial, tangential, and vertical to the circle edge during a circle drawing task. We employed varying directional (clockwise vs. counterclockwise) and pacing (self-paced vs. external-paced) conditions. Results showed that synergies between pen-hand contact forces existed in all components. Radial and tangential component synergies were greater than in the vertical component. Synergies in the clockwise direction were stronger than the counter-clockwise direction in the radial and vertical components. Pace was found to be insignificant in all conditions.